For decades, men have been encouraged to undergo routine checkups to detect prostate cancer in its earliest stage. This usually includes the test for prostate-specific antigen (PSA). The amount of this protein in the bloodstream climbs when a tumor begins growing in the prostate gland.

In theory, detecting a prostate tumor early should save lives. But the longest-running trial to date shows that checking PSA levels in seemingly healthy men does little to cut a man’s chances of dying of the disease.